Gordon Brown is about to make a speech to the specialist schools and academies trust. It is, we are told, a "keynote speech on social mobility", serving further notice of the fact that even if his prospects are grim and getting grimmer, the PM is still set on "tackling systemic inequality in Britain".

But how the advance stories differ. For the Guardian, the big talking point is a plan for "payments to tackle child poverty" – one-off, £200 rewards apparently to be given to low-income families who take up offers of government help and make sure their children get the right immunisation jabs. Over at the Telegraph, news of Brown's turn is headlined "Gordon Brown blames Margaret Thatcher for poor social mobility", with an emphasis on his allegations that "Thatcher's children" represent a "lost generation" (and, somewhat inevitably, another outing for a picture of the Browns welcoming her for tea last summer). The Times, meanwhile, goes for "Britons need better work ethic to get ahead, Gordon Brown says", which tees up the following, rather head-turning paragraph: "Mr Brown, a notorious workaholic, is expected to tell an event in London that parents must want their children to do better than they did themselves but that this 'cannot be achieved without people themselves adopting the work ethic, the learning ethic and aiming high ... We must set a national priority to aggressively and relentlessly develop the potential of the British people.'"

At which point, one's heart sinks, and the temptation to once again have a pop at the PM becomes pretty much irresistible. The problems here include the usual crypto-Stalinist mode of speech ("We must set a national priority to aggressively and relentlessly develop the potential of the British people" – shades, once again, of the Soviet Union circa 1929), and the standard New Labour failure to extend any conversation about inequality and social mobility towards the super-rich elite to whom the government endlessly genuflect. But even more depressing is the fact that the government – indeed, the entire political class – cannot have any conversation about those at society's blunt end without being seen to implicitly upbraid them for their lack of that all-important motivation to somehow "work hard and get on".

Some counter-arguments, then. Contrary to the idea that hopelessness goes hand in hand with worklessness, half of British children in poverty live in a household containing at least one working adult. No matter what their levels of hard work and aspiration, teenage apprentices in such sectors as early years care, retail and business administration often take home less than £80 a week. Higher up the age range, according to one survey by the TUC, one in three people claim that "long hours or stress" prevent them engaging in in-job training and moving up the workplace ladder. And small wonder: Britons, despite their alleged need of "a better work ethic", put in some of the longest hours in western Europe.

But here's the interesting thing. Ask kids in some of our most outwardly deprived areas about their aspirations, and the alleged absence of a "learning ethic" – let alone the tendency to "aim high" – often fails to materialise. Some very interesting figures for the London borough of Barking and Dagenham recently arrived in my inbox, taken from a 2007 Ofsted survey entitled TellUs2 (pdf). According to its figures, 53% of local school children say they hope to go to university; 86% say they try their best at school, either always or most of the time, and more than half say they enjoy school. Exams, the survey discovered, represent local kids' single biggest worry.

Look at the local job market, however, and you begin to understand what happens to too many of those hopes. The point is not that aspiration is lacking; it's that it bumps up against a low-end economy that has no use for it, and gets swiftly squashed. Therein lies the glaring hole in Brown's speechifying, and a depressingly familiar spectacle: a high-up politician exhorting people to develop their potential and reach for the stars, against a backdrop of far too many low-quality, "flexible" jobs, and the dead-end prospects they embody. As usual, on that subject, the silence is deafening.